1. Technical Field
The invention relates to purification methods and systems related to renewable materials and biofuels production. Aspects of the invention relate to the recovery of products from a fermentation process.
2. Discussion of Related Art
Renewable materials can be derived from biotic feedstocks in a process such as by fermentation. Biotic feedstocks include polysaccharide-containing plants, such as sugarcane, lignocellulosic biomass, corn, wheat, and others. Fermentation is catalyzed by micro-organisms grown in fermentation broth, where the fermentation broth includes sugars derived at least in part from the polysaccharides of the biotic feedstock. Micro-organism activity and efficiency are generally susceptible to the conditions of the fermentation broth, such as the pH and the presence of organic acids, salts, metals, and vitamins. The renewable material produced is often inhibitory to microbial activity, such as with fermentation to produce alcohols. As a fermentation progresses, inhibitory levels of the renewable material can be reached at low product concentrations. For example, typical product concentrations at which significant inhibition occurs for ethanol and butanol fermentations are 10% by weight and 2% by weight, respectively.
Purification of renewable materials from low concentrations requires considerable equipment, and also significantly affects the overall energy-integration of a fermentation process. Renewable materials can be purified by several means including by boiling point difference, such as distillation. Distillation, such as distillation of a renewable material with a lower boiling point than water, includes heating the fermentation broth to above the boiling point of the renewable material and condensing the hot vapors of concentrated renewable material.
Purification of renewable materials from low concentration fermentations can be accomplished but with significant expenditure of equipment and energy. There is a need and desire for more efficient processes and systems for purifying renewable materials. There is a further need and desire for processes and systems for converting biomass to biofuels that require minimal energy.